The long term objective is to develop a new technology for industry scale affinity separations employing proprietary Bio-Receptor ferrofluids (BR-FF) in combination with existing continuous high gradient magnetic separators (HGMS) and improved systems currently being developed. BR-FF are being used with HGMS successfully for doing immunoassays and together they represent a significant step forward in the field offering numerous advantages over prior systems. The specific aims of this proposal are to determine if BR-FF as currently synthesized or as synthesized by relatively straightforward modification can withstand the rigors of desorption (low pH, denaturants, Kaotropic ions) and recycling. Affinity separations currently play a minor role in bioprocessing in part because of cost and the nature of affinity supports (particles or membranes) which are constrained to batch mode and ultra clean solutions. BR-FF and HGMS offers the potential for continuous affinity separation which can function in the presence of major solution contaminents including solids; thus a new bioprocessing technology which also requires significantly less processing steps is possible.